The invention relates to a pacing electrode arrangement for a pacemaker.
Implanted pacemakers in connection with pacing electrodes, arranged on an intracardiac electrode catheter and positioned on the heart inside wall, have long been used for the treatment of various chronic arrhythmias. They are designed to stimulate the excitable cardiac tissue, thereby compensating defects in the body's own cardiac stimulus generating and conduction system.
The designs for pacemaker and associated electrodes have been improved more and more. Numerous technical solutions for attaching the electrode leads to the heart wall--in the ventricle as well as the atrium--have been discovered and essential practical improvements have actually been made, with the goal of ensuring good, long-term contact between the pacing electrode(s) and the heart tissue, so as to achieve simultaneously an energy-saving and secure stimulation.
Nevertheless, the dislocation of electrodes is still considered one of the most serious complications encountered in pacemaker therapy, which results in a worsening or a loss of contact with the heart to be stimulated on the inside wall and consequently increases the stimulus threshold considerably, thus leading to an increased current consumption of the pacemaker as well as a reduced life expectancy and, in the worst case, to the operational failure of this pacemaker. The technical development of attachment mechanisms (becoming ever more complicated and expensive) therefore still continues.
In addition to high production costs, these traditional electrode arrangements have the disadvantage of requiring a great deal of experience and expenditure for the implantation.
Also known are electrode arrangements, which are not intended for a permanent attachment in the ventricle or the atrium (so-called "floating" arrangements) and are easier to implant, are cheaper and require less knowledge for the implantation. These electrode arrangements are known primarily from implantable defibrillator arrangements, but are also used with pacemakers.
An early arrangement of this type is disclosed in the U.S. Pat. No. 3,915,714.
The European Patent Application EP 0 601 338 A1 describes an electrode system for an implanted defibrillator, comprising at least two intravascular positioned coil electrodes (spiral-type electrodes), held in place without special fasteners, simply because of their size. One of these large-surface defibrillation electrodes can be arranged specifically in the vena cava superior.
The European Patent Application EP-O 677 301-A1 discloses an electrode catheter for use with a defibrillator, which comprises an elongated, cylindrical electrode with a covering that can be moved along the electrode lead, thereby permitting a displacement of the effective electrode region. For example, the catheter can be adjusted such that a first electrode is positioned in the ventricle and that the electrode region, positioned through movement of the covering, is located in the vena cava superior.
In past clinical experiments, pacing electrodes that float in the heart could not ensure with sufficient certainty a reliable stimulation, given the available stimulus pulse voltage and making economic use of the limited battery capacity, to allow for a worthwhile practical operation.
Apart from the aforementioned practical problems, the traditional method of transmitting the stimulation pulses from an implanted pacemaker via electrodes installed in the wall to the excitable muscle tissue of the heart inside wall, in the lower region of the ventricle or the atrium, cannot lead to satisfactory results in a number of frequently occurring arrhythmias, owing to basic physiological considerations. This procedure is designed to stimulate regions in the lower hierarchical planes of the cardiac stimulus generating and conduction system. The procedure can require, for example, a technically involved two-chamber stimulation (in the atrium and ventricle), even for clinical pictures shaped by a sinus node defect, but where the remaining stimulus conduction system is for the most part intact.
The applicant's DE Patent Application 196 09 471.2 relates to an arrangement with preferably floating pacing electrodes of varied polarity, designed to produce a stimulus pulse field that is "focused" onto predetermined heart tissue regions.